Sink



FIG. 1 is a front perspective view of a sink, showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a left side elevation view thereof; and,

FIG. 6 is a rear elevation view thereof. 

The ornamental design for a sink, as shown and described. 